Streaming Media

 

Xstream MultiCaster: Streaming Appliance with Muscle
Winnov’s entry into the streaming capturer/encoder/server appliance market has a lot to offer large customers, but may not be right for everyone. Contributor Jabar McKellar puts the MultiCaster through its paces.
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Winnov (www.winnov.com) has come through with another desirable A/V-over-IP solution in the form of a 1U rack-mountable appliance. "The Xstream MultiCaster is the first software encoder in a one-unit rack-mountable chassisspecifically designed for professional webcasters," chirps the brochure.

That may be true, but let's clear something up right out of the gates: The unit does not multicast — it encodes and broadcasts multiple streams simultaneously, but it does not multicast. That’s just a product name issue though, because the Xstream MultiCaster works as advertised, and in some ways (it includes a software vector scope, for instance), it raises the bar for encoding and delivery appliances.

The Xstream MultiCaster comes with a six-foot DVI cable connected to the same breakout box delivered with Winnov's Videum II Broadcaster board (See Review). For video, there are four BNC connectors that can be allocated as up to four composite inputs and up to two S-video inputs (using a cable to connect each pair of BNC connectors to an S-video adapter). All audio I/O is for professional balanced audio, provided in stereo pairs: two combo XLR 0.25-inch input jacks, two separate 0.25-inch input jacks, and two 0.25-inch output jacks for monitoring. The allocation of the A/V inputs is software-switchable — on the fly. Up to four of the rack-mountable breakout boxes can fit in a single 19-inch mounting bracket.

We were very impressed with the OEM server chosen by Winnov to power this system. The server-class box has a very nice BIOS setup (from American Megatrends) for the motherboard, complete with realtime fan speed and CPU temperature indication for the beefy dual-933MHz Pentium IIIs. The unit we tested had a single 28GB Maxtor IDE drive, but shortly, the Xstream MultiCaster will ship with two hot-swappable drives, complete with software-based RAID for striping or mirroring. The system also features dual Intel Pro/100 network interface cards, which professional broadcasters can allocate to separate networks to allow failover, should one connection go belly-up.


Easy Installation and Setup

We installed and tested this shipping model at the San Francisco facilities of ITN SignalStream (www.itnsignalstream.com). Those who are interested in streaming infrastructure build-outs on any scale will be happy to know that there are no tricky rack rails, wire-minders or proprietary screw patterns and adapters with this box — rack-mounting was easy. It may seem like a minor point, but those who have worked in data centers know that trouble-free rack-mounting is anything but a foregone conclusion with new hardware.

The ITN SignalStream broadcast engineers ran us several feeds from professional sources, such as an analog satellite receiver (KU band). Within a few minutes, we had two video sources and two matching audiosources hooked up to the Xstream MultiCaster.

The system booted up and started all the appropriate applications as documented, including a "demo templates" folder to get us started. When we used the Winnov Utilities to assign the first video input, we took the time to get familiar with the included software vector scope, which comes complete with chroma and luma adjustments. Yeah, that’s right — a software vector scope and, in fact, a nice one with a video preview. By contrast, a hardware vector scope (a specific kind of oscilloscope used to set up and monitor the color reproduction of a video signal) can run $6,000 or more.


Live Streaming in Seconds

Balanced Media Streaming (BMS) is a new feature from Winnov, similar in concept to Microsoft’s Multiple Bit Rate and RealNetworks’ SureStream technologies, that takes one A/V master and produces multiple instances of an encode in chosen bit rates. The distinguishing capability of Winnov’s BMS is that it lets you customize each individual stream with every option available, which makes a world of difference, as you’ll read below.

Double-clicking the "Start Streaming Media Balancing" batch file starts the four pre-configured Windows Media 7 Encoder templates: 160 by 120 at 15 frames per second and 28Kbps on port 8028; 176 by 144 at 15fps and 50Kbps on port 8050; 240 by 180 at 130fps and 100Kbps on port 8100; and 320 by 240 at 30fps and 300Kbps on port 8300. These are just templates, any configuration of four streams is possible in WM7 or Real8, though QuickTime is not supported at all. Microsoft’s WM8 is exclusively command-line driven and said to be much faster than WM7 at encoding, but the Xstream MultiCaster currently supports only WM7. Because it’s a Windows 2000 system, support for WM8 is likely to follow soon.

Although CPU load was only at about 52 percent during the capture, encode and serve operation, we did not hit the expected frames per second on the 100Kbps, 50Kbps or 28Kbps streams, resulting in very choppy video. We did hit expected bit rates on all streams, though. This explains why the frame rates had to drop: A well-mannered encoder will not exceed the specified bit rate.

To fix the problem, we stopped all streams and went into the WM7 templates to tweak image quality and key frame intervals. After tweaking, CPU usage went up to 75 percent, but the streams hit all frame rate marks within a 5 percent loss margin. This is just one of the many trade-offs encoders must make, and the ability to make choices separately for each stream is nice — the BMS is action.

When testing in Real format, with the exact same pre-configured templates, we experienced the same initial problem, but were able to effect more or less the same resolution — by tinkering with encoding parameters for each stream as enabled by BMS. The process for modifying the Real parameters was a bit different, however, as Real uses a batch configuration model. We had to make our changes by editing a text file. This does have an advantage, though: The Real Producer GUI doesn’t open when encoding, saving a tremendous amount of CPU power. Once again, the BMS was useful.

In our tests, with all four streams running, the CPU load held at about 15 percent in both the pre- and post-tinkering tests. In this case, the BMS was more about optimizing each stream than reducing CPU utilization.

Although encoding is a science, it often feels much more like an art because of the trade-offs that have to be made. Winnov helps by including the Real Producer Plus 8.5 Users Guide and a third-party bookon Windows Media ("Inside Windows Media"). This may not sound very remarkable, but most of us got through the novice stage of encoding through trial and error and would have found this little extra a huge time saver. Unfortunately, the Winnov support was partly down when I visited, and the parts that were up didn’t have the information I sought. It may have been in the Online Interactive Troubleshooting database section that was marked as temporarily down when I visited.


Bang for the Buck

Once your personal touches have been added to the encoding properties, you can run "Auto Start Balanced Streaming." One nice feature here to note: In the event of a server crash, when the system reboots, the streams will automatically start with all your settings intact – if you are running "Auto Start Balanced Streaming."

We checked the audio and video quality throughout the entire process and noticed that Winnov hasn’t lost its touch. If you have quality video going in, this box seems to reproduce the quality digitally. The balanced audio is impressive, as well.

Although we tested this model in one of the most advanced signal acquisition facilities on the West Coast, almost none of the traditional broadcast equipment was needed. All signal processing in audio and video were set to bypass, so we were feeding the Winnov an untreated source. The software vector scope is a powerful touch, and onboard audio compression eliminated the usual need for a hardwarelimiter/compressor.

There is one component that you may still need, though — a traditional A/V router or switch. When I switched the live audio and video feeds to different sources through the Winnov software, there was a three-second re-buffer delay. Further, the Winnov preview window did not reset for about five seconds, and even then there was no way to audibly check the volume quality natively. So, Winnov’s software-based switching is great for configuration, testing, and verification, but it does not replace a traditional switch.

The Xstream MultiCaster is built for professional broadcasters like CDNs, traditional broadcast stations, ISPs and corporate enterprises. Compared to building a similar custom system in-house, the Xstream MultiCaster is an excellent choice for just about all of the aforementioned company types. However, at $10,000, it’s a purchase that probably should be evaluated against a company’s requirements,and against the competition in the capturer/encoder/server appliance market – a space moving so fast that it’s hard to get a good picture of all the players at once.

The Xstream MultiCaster is clearly a good machine, though, and definitely merits consideration on your short list. The engineering design and execution is impressive. Like other Winnov products we've tested, it’s reliable. The documentation is strong via the encoding manuals included, though support may be a little lacking. Performance and ease of use are very good. And the quality of the audio and video capture is excellent.